The objective of this proposal is to understand the molecular basis for the biological functioning of porphyrin systems. There are six specific types of work: (1) We are studying the optical absorption and luminescence spectra and the electronic structure of exotic metalloporphyrins; (2) we are studying the zero field splitting of the triplet state of metal pophyrins; (3) we are studying fast kinetic processes in the psec and nsec time domain--for example electron transfer from an excited porphyrin to an electron acceptor such as quinone; (4) we are studying the optical and electrical properties of porphyrin films made by vapor deposition; (5) we are studying the electronic spectra and structure of covalently linked porphyrin dimers, such as the micron- oxo dimer of Sc(III); (6) we hope to synthesize and study iron porphyrins with fifth and sixth ligands covalently linked by side chains.